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Synthesis of High Molecular Weight Polyethylene and E-MA Copolymers Using Iminopyridine Ni(Ⅱ) and Pd(Ⅱ) Complexes Containing a Flexible Backbone and Rigid Axial Substituents

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Chinese Journal of Polymer Science 2023年第2期41卷 233-239页

作者： yu-Dan Liao Qi Cai Sheng-yu dai School of Chemical and Environmental Engineering Anhui Polytechnic UniversityWuhu241000China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefei230601China

Suppressing the chain transfer reactions during polymerization in late-transition metal-catalyzed olefin polymerization systems is the key to obtaining high molecular weight polyolefin materials. In this work, two efficient strategies(“sandwich” and rotation-restricted strategies)to retard chain transfer reactions in ethylene(co)polymerization were employed for the iminopyridyl system. Herein, a family of iminopyridyl Ni(Ⅱ)and Pd(Ⅱ) complexes with a flexible backbone and rigid axial bulky aryl substituents were designed, synthesized and characterized. In ethylene polymerization, the iminopyridyl Ni(Ⅱ) and Pd(Ⅱ) catalysts using the two strategies exhibited reasonable activities and generated highly branched polyethylenes with high molecular weights, where catalysts with dibenzosuberyl substituents exhibited significantly higher activities and produced higher molecular weight polyethylene than catalysts with 8-arylnaphthalenyl substituent. A similar trend of activities and molecular weights was also found in the copolymerization of ethylene with MA using the Pd(Ⅱ) catalysts. Moreover, highly branched E-MA copolymers with moderate to high molecular weights and high incorporation ratios(up to 17.4 mol%) were generated with the two Pd(Ⅱ) catalysts. Most interestingly, as compared with the dibenzhydryl Ni(Ⅱ) and Pd(Ⅱ) catalysts, the catalysts using the two strategies exhibited a superior ability to retard the chain transfer reactions and generated polymers and copolymers with 1-2 orders of magnitude higher molecular weights during ethylene(co)polymerization.

关键词： Ni(Ⅱ)and Pd(Ⅱ) Suppressing chain transfer High molecular weight Ethylene(co)polymerization

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Flow field effect of delayed neutron precursors in liquid-fueled molten salt reactors

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Nuclear Science and Techniques 2022年第8期33卷 16-32页

作者： Xian-Di Zuo Mao-Song Cheng yu-Qing dai Kai-Cheng yu Zhi-Min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

In molten salt reactors(MSRs),the liquid fuel salt circulates through the primary loop and a part of the delayed neutron precursors(DNPs)decays outside the reactor *** model and analyze the flow field effect of DNPs in channel-type liquid-fueled MSRs,a three-dimensional space-time dynamics code,named ThorCORE3D,that couples neutronics,core thermalhydraulics,and a molten salt loop system was developed and validated with the Molten Salt Reactor Experiment(MSRE)*** effects of external loop recirculation time,fuel flow rate,and core flow field distribution on the delayed neutron fraction loss of MSRE at steadystate were modeled and simulated using the ThorCORE3D ***,the flow field effect of the DNPs on the system responses of the MSRE in the reactivity insertion transient under different initial conditions was analyzed systematically for the channel-type liquid-fueled *** results indicate that the flow field condition has a significant effect on the steady-state delayed neutron fractions and will further affect the transient power and temperature responses of the reactor *** analysis results for the effect of the DNP flow field can provide important references for the design optimization and safety analysis of liquid-fueled MSRs.

关键词： Molten salt reactor Delayed neutron precursor Nodal expansion method Coupled neutronics and thermal-hydraulics

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A NOTE ON THE NONLINEAR CONJUGATE GRADIENT METHOD

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Journal of Computational Mathematics 2002年第6期20卷 575-582页

作者： dai, yu-hong yuan, Ya-xiang Chinese Acad Sci Acad Math & Syst Sci Inst Computat Math & Sci Engn Comput State Key Lab Sci & Engn Comput Beijing 100080 Peoples R China

Discusses several aspects of the linear conjugate gradient method for unconstrained optimization problems. General condition concerning the scalar; Convergence of the famous Fletcher-Reeves and Polak-Ribiere-Polyak co... 详细信息

关键词： unconstrained optimization conjugate gradient line search global convergence

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A New Analysis on the Barzilai-Borwein Gradient Method

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Journal of the Operations Research Society of China 2013年第2期1卷 187-198页

作者： yu-Hong dai State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific/Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of SciencesP.O.Box 2719Beijing 100190P.R.China

Due to its simplicity and efficiency,the Barzilai and Borwein(BB)gradi-ent method has received various attentions in different *** paper presents a new analysis of the BB method for two-dimensional strictly convex quadratic *** analysis begins with the assumption that the gradient norms at the first two iterations are *** show that there is a superlinear convergence step in at most three consecutive ***,we provide a better convergence relation for the BB *** influence of the starting point and the condition number to the convergence rate is comprehensively addressed.

关键词： Unconstrained optimization Barzilai and Borwein gradient method Quadratic function R-superlinear convergence Condition number

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Assembly of a Heteronuclear POM {[K_(5)Na_(6)Cu^(Ⅱ)_(5)(CH_(3)COO)_(20)(CH_(3)CN)]Cl}_(n) via Two Kinds of Clusters as the Basic Bridge Unit

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Chinese Journal of Structural Chemistry 2018年第10期37卷 1612-1618页

作者： dai yu-Mei XU Jie Minnan Science and Technology Institute Fujian Normal UniversityQuanzhou 362332China

A novel 3D hetero-nuclear framework,namely{[K_(5)Na_(6)Cu^(Ⅱ)_(5)(CH_(3)COO)_(20)(CH_(3)CN)]Cl}_(n)(1),was obtained by hydrothermal *** metal centers(including sodium/potassium or/and copper)were coordinated to acetate anions in such two heteronuclear clusters,***,nine kinds of binding modes for acetate anions were illustrated in polymer 1,with the first reported pentadentate coordination mode for acetate ligand.

关键词： hydrothermal synthesis acetate Hgand heteronuclear clusters of sodium/potassium and copper

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On the complexity of sequentially lifting cover inequalities for the knapsack polytope

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Science China Mathematics 2021年第1期64卷 211-220页

作者： Wei-Kun Chen yu-Hong dai School of Mathematics and Statistics Beijing Institute of TechnologyBeijing100081China LSEC ICMSECAcademy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing100049China

The well-known sequentially lifted cover inequality is widely employed in solving mixed integer ***,it is still an open question whether a sequentially lifted cover inequality can be computed in polynomial time for a given minimal cover(Gu et al.(1999)).We show that this problem is N P-hard,thus giving a negative answer to the question.

关键词： integer programming sequentially lifted cover inequality complexity lifting problem

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Method of SLAS’s ground track manipulation based on tangential impulse thrust

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Journal of Systems Engineering and Electronics 2023年第5期34卷 1285-1293页

作者： LE Xinlong CAO Xibin dai yu WU Fan School of Astronautics Harbin Institute of TechnologyHarbin 150001China

Satellites with altitudes below 400 km are called super low altitude satellites(SLAS),often used to achieve responsive imaging ***,it is important for the manipulation of its ground *** at the problem of ground track manipulation of SLAS,a control method based on tangential impulse thrust is ***,the equation of the longitude difference between SLAS and the target point on the target latitude is derived based on Gauss’s variational *** this basis,the influence of the tangential impulse thrust on the ground track’s longitude is ***,the method for ground track manipulation of SLAS under the tangential impulse thrust is *** simulation results verify the effective-ness of the method,after manipulation,the satellite can visit the target point and revisit it for multiple days.

关键词： super low altitude satellite(SLAS) ground track drift modeling ground track manipulation tangential impulse thrust

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NUMERICAL STUDY ON THE PURIFICATION PERFORMANCE OF RIVERBANK

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Journal of Hydrodynamics 2007年第5期19卷 643-652页

作者： dai yu WANG De-guan College of Environmental Science and Engineering Hohai University Nanjing 210098 China

During the rain time, the runoff infiltrates into the riverbank through the collecting gutter and slope surface. The city runoff is generally polluted by organic, oil, heavy metal particulates, etc. The pollutants moving with the water through the riverbank experience advection, dispersion, diffusion, adsorption, biochemical reaction and plant uptaking processes. In this article, a mathematical model was developed to simulate the performance of pollutant removal of the riverbank. The model took those main mechanisms into account. The modified Richards equation was used in simulating flow field. The mass balance law was employed in deriving the equation for pollutant transport, where the diffusion and dispersion were described with the Fick-type law, the adsorption was macroscopically expressed as form isotherm, and the bio-chemical degradation process was assumed to follow the Monod kinetics. The NH3-N and TP were considered in the present model. The mathematical model was descritized with a finite element numerical model, which was applied to two types of model riverbanks. In the model test, the hydraulic loading was assumed to have the intermittent pattern simulating the storm runoff of certain return period, and the values of the rainfall runoff and concentrations of the NH3-N and TP were taken from the model test. The computed overall removal rates for the NH3-N and TP in 6 cases are in the range of 88%-98%, 87%-97%, respectively. The differences between the computed and tested overall removal rates for the NH3-N and TP are less than 5%. The time-varying oscillation pattern of the concentrations of the NH3-N and TP were rationally simulated, which shows that the model presented in this article can be used to assess the purification performance of the riverbank constructed with sand or soil.

关键词： riverbank numerical modelling purification,pollutant experiments

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MapReduce Scheduler by Characterizing Performance Interference

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China Communications 2016年第10期13卷 253-262页

作者： Lei Yang yu dai Bin Zhang College of Computer Science and Engineering Northeastern University China College of Software Northeastern University China

Recently, virtualization has become more and more important in the cloud computing to support efficient flexible resource provisioning. However, performance interference among virtual machines(VMs) has become a challenge which may affect the effectiveness of resource provisioning. In a virtual cluster which runs the Map Reduce applications, the performance interference can also affect the performance of the Map and Reduce tasks and thus cause a performance degradation of the Map Reduce job. Accordingly, this paper presents a Map Reduce scheduling framework to mitigate this performance degradation caused by the performance interference. The framework includes a performance interference prediction module and an interference aware scheduling algorithm. To verify its effectiveness, we have done a set of experiments on a 24-node virtual Map Reduce cluster. The experiments illustrate that the proposed framework can achieve a performance improvement in the virtualized environment compared with other Map Reduce schedulers.

关键词： Map Reduce scheduler performance interference

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Solution to an Extremal Problem on Bigraphic Pairs with a Z3-connected Realization

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Acta Mathematica Sinica,English Series 2017年第8期33卷 1131-1153页

作者： Jian Hua YIN Xiang yu dai Department of Mathematics College of Information Science and TechnologyHainan UniversityHaikou 570228P.R.China

Let S = （a1,...,am;b1,...,bn）, where a1,...,am and b1,...,bn are two nonincreasing sequences of nonnegative integers. The pair S= （a1,..., am; b1,..., bn） is said to be a bigraphic pair if there is a simple bipartite graph G = （X ∪ Y, E） such that a1,…, am and b1,..., bn are the degrees of the vertices in X and Y, respectively. Let Z3 be the cyclic group of order 3. Define σ（Z3, m, n） to be the minimum integer k such that every bigraphic pair S = （a1,..., am; b1,..., bn） with am, b ≥ 2 and σ（S） = a1 ＋ ... ＋ am ≥ k has a Z3-connected realization. For n = m, Yin [Discrete Math., 339, 2018-2026 （2016）] recently determined the values of σ（Z3,m,m） for m ≥ 4. In this paper, we completely determine the values of σ（Z3, m, n） for m ≥ n ≥4.

关键词： Bigraphic pair Z3-connected realization group connectivity

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